1. Field of the Invention
The present invention relates to a flash device, a lens-fitted photo film unit, a camera, a light measuring device, and a method of producing lens-fitted photo film unit. More particularly, the present invention relates to a flash device of which circuit elements can be disposed in an economized space, and a lens-fitted photo film unit, a camera, a light measuring device, and a method of producing lens-fitted photo film unit in connection with the structure of the flash device.
2. Description Related to the Prior Art
A lens-fitted photo film unit is well-known, which is pre-loaded with unexposed photo film, and is easily used for taking an exposure as soon as a user purchases it. There are types of the lens-fitted photo film unit having a built-in flash device, which can illuminate a photographic field even at night or indoors. The flash device is a unified device in which circuit elements for flash emitting operation are mounted on a single circuit board. Among the plural types of the lens-fitted photo film unit, the flash device is used as a common part.
As the lens-fitted photo film unit has a simplified and small construction, an aperture stop is fixed. An underexposed or overexposed condition is likely to occur according to an amount of light of a scene. To solve such a problem, there have been proposals to incorporate an exposure adjusting structure in the lens-fitted photo film unit. It is preferable to automate the control of the exposure in consideration of users unskilled in handling of a camera. Thus, there is a suggestion of incorporating a light measuring circuit in the lens-fitted photo film unit for the AE control.
An example of controlling an exposure by the light measuring circuit is an auto flash device, which is the flash device of an automatic light adjusting structure for preventing an object from being photographed with an excessively whitish manner, which occurs typically in close-up photography with flash at a near distance. The auto flash device measures reflected flash light from the object, effects integration, and quenches emission of flash light when the integrated light amount comes up to a predetermined level.
If the single circuit board is provided with circuit elements for the purpose of providing the flash device with a structure for effecting photometry, it is necessary to dispose the circuit elements in a high mounting density, or to enlarge the area of the circuit board. If a manufacturer intends considerably high density of mounting the circuit elements, precision in the assembling the circuit elements or in wire printing of the circuit board must be high. This causes an unwanted increase in the manufacturing cost.
If one intends enlargement of the circuit board, the lens-fitted photo film unit must have a larger size itself. There occurs a problem in that the compact feature of the lens-fitted photo film unit is lost. Furthermore, a problem in the manufacture lies in that the flash device with the light measuring circuit must be produced in a manner separate from the flash device without the light measuring circuit. It is impossible to use the flash device commonly between types of the lens-fitted photo film unit, as the circuit board cannot be readily treated board by board.
In view of the foregoing problems, an object of the present invention is to provide a flash device of which circuit elements can be disposed in an economized space, and can have compatibility between plural types of flash built-in optical instrument, and a lens-fitted photo film unit, a camera, a light measuring device, and a method of producing lens-fitted photo film unit in connection with the structure of the flash device.
In order to achieve the above and other objects and advantages of this invention, a flash device comprises a main capacitor for storing charge at high voltage for emission of flash light. A main circuit board is connected with the main capacitor, and has a main circuit element group mounted thereon, the main circuit element group being adapted for the flash emission. A subsidiary circuit board is connected with the main circuit board, and has an auxiliary circuit element mounted thereon, the auxiliary circuit element operating in an auxiliary manner to the main circuit element group.
Furthermore, a flash discharge tube is connected with the main capacitor, for emitting the flash light by discharge at the high voltage. The main circuit element group includes a booster circuit connected with the main capacitor, for boosting power source voltage to obtain high voltage. A trigger circuit triggers the discharge of the flash discharge tube in response to an exposing operation.
The main capacitor includes a pair of capacitor terminal pins by which the main and subsidiary circuit boards are connected with one another.
The subsidiary circuit board is oriented substantially perpendicularly to the main circuit board.
The auxiliary circuit element constitutes a flash quenching circuit for obtaining a light amount of reflected light from a photographic field illuminated by the flash light, and for outputting a quench signal for discontinuing operation of the flash discharge tube upon a reach of the light amount at a predetermined level.
The main circuit element group further includes a sync switch for being turned on in synchronism with the exposing operation, to operate the trigger circuit. Furthermore, a photometric element is mounted on the subsidiary circuit board, for measuring the reflected light from the photographic field illuminated by the flash light, and for outputting a photometric signal. The flash quenching circuit obtains the light amount by integration of the photometric signal.
According to another aspect of the invention, a flash device comprises a booster circuit for boosting power source voltage to obtain high voltage. A main capacitor for stores charge at the high voltage. A flash discharge tube is connected with the main capacitor, for emitting flash light by discharge at the high voltage. A trigger circuit triggers the discharge of the flash discharge tube in response to an exposing operation. A main circuit board has the booster circuit and the trigger circuit mounted thereon. A photometric element measures reflected light from a photographic field illuminated by the flash light, and for outputting a photometric signal. A flash quenching circuit obtains a light amount by integration of the photometric signal, and for outputting a quench signal for discontinuing operation of the flash discharge tube upon a reach of the light amount at a predetermined level. A subsidiary circuit board is connected with the main circuit board, and has the photometric element and the flash quenching circuit mounted thereon, the main capacitor being connected with the subsidiary circuit board electrically and in a firmly fastened manner.
Furthermore, a choke coil has one end portion connected with the main capacitor, and a remaining end portion connected with a circuit element included in the flash quenching circuit, for protecting the circuit element from a current of a high frequency generated upon the discharge of the main capacitor.
Furthermore, a bobbin is secured to an outer surface of the main capacitor, for winding the choke coil thereabout. The subsidiary circuit board and the main capacitor constitute a main capacitor unit.
Furthermore, a projection is formed on the bobbin, for positioning the subsidiary circuit board on the main capacitor.
The main capacitor includes a pair of capacitor terminal pins by which the main and subsidiary circuit boards are connected with one another.
In another preferred embodiment, the subsidiary circuit board includes a pair of line-shaped subsidiary board terminal patterns by which the main circuit board and the main capacitor are connected with one another.
In still another preferred embodiment, furthermore, a photoreceptor element measures ambient light from the photographic field. An exposure control circuit is mounted on the main circuit board, for sending an ambient light state signal to the flash quenching circuit according to an output from the photoreceptor element. The flash quenching circuit determines the predetermined level of the light amount of the reflected light in consideration of the ambient light state signal.
The subsidiary circuit board is fastened on the main circuit board in a direction perpendicular thereto. The exposure control circuit includes an output terminal disposed on a contact surface of the main circuit board opposed to the subsidiary circuit board, for outputting the ambient light state signal. The flash quenching circuit includes an input terminal disposed on a contact surface of the subsidiary circuit board opposed to the main circuit board, and connected with the output terminal.
According to still another aspect of the invention, a flash device includes a discharge tube case, secured to the main circuit board, for containing the flash discharge tube. A subsidiary circuit board is connected with the main circuit board, secured to the discharge tube case, and has the photometric element and the flash quenching circuit mounted thereon, the main capacitor being connected with the subsidiary circuit board electrically and in a firmly fastened manner.
Furthermore, a support plate is secured to the discharge tube case, for retaining the subsidiary circuit board.
The support plate is secured to a rear of the discharge tube case to extend substantially in parallel with the subsidiary circuit board.
According to another aspect of the invention, a lens-fitted photo film unit of a flash built-in type is provided, is pre-loaded with photo film, and includes the flash device of the above construction.
Furthermore, a main body has the main and subsidiary circuit boards secured thereto, has a cassette holder chamber and a photo film chamber, the cassette holder chamber being loaded with a photo film cassette, the photo film chamber being loaded with photo film from the photo film cassette in a roll form. Front and rear covers cover respectively a front and a rear of the main body. An externally operable charger button is disposed in the front cover. A charger power switch is disposed behind the charger button, for being turned on by operation of the charger button, to power the booster circuit.
According to a further aspect of the invention, a camera of a flash built-in type is provided, and includes the flash device of the above construction.
According to another aspect of the invention, a producing method of producing a lens-fitted photo film unit is provided. In the producing method, the flash device is set between the main body and the front cover by positioning the charger power switch at the charger button, positioning the sync switch relative to the shutter blade, and positioning the photometric element at the photometric window. After the flash device is set, the photo film cassette is set into the cassette holder chamber, and the photo film into the photo film chamber.
Furthermore, a middle of a pair of terminal pins of the main capacitor is attached to the subsidiary circuit board by insertion through holes or grooves in the subsidiary circuit board and by soldering. An end of the terminal pins is attached to the main circuit board by soldering, to combine the main and subsidiary circuit boards with one another by the terminal pins.
Furthermore, the subsidiary circuit board is connected with the main capacitor, to constitute a main capacitor unit together therewith. The main capacitor unit is connected with the main circuit board, to constitute the flash device together therewith.
According to an additional aspect of the invention, a light measuring device for automatic flash control is provided. A photometric element measures reflected flash light. A photometric element cover covers the photometric element. An entrance opening is formed in the photometric element cover, for introducing the flash light to the photometric element. A light reducing filter is incorporated in the photometric element cover, disposed between the photometric element and the entrance opening, for reducing the flash light traveling to the photometric element.
Consequently, the dual board structure is provided in the flash device, the lens-fitted photo film unit and the camera. The circuit elements can be disposed in an economized space, and can have compatibility between plural types of flash built-in optical instruments.